In women, during menstruation, we often see cutaneous eruptions, as acne or hives. The former is often very distressing in boys and girls in the years of puberty, and it is quite impossible to deny that this may be a symptom of a hyperactivity of the sexual glands. Thus, we often observe acne in persons who are masturbating, or who for a long time live in complete sexual abstinence, so that in certain places the laity term these “pimples of chastity.” Here, again, married life is the best cure for this disease, as it is for so many others. It is very interesting to note during the question we are now discussing that persons suffering from psoriasis feel relief from their affection when they have had a good opening of the bowels, or when they perspire freely; hence in hot summer weather they suffer less inconvenience than in the winter; also by following a certain diet this disease may be favorably influenced; that is to say, such persons have fewer psoriatic patches when the toxic products are eliminated by the intestines or kidneys. When there is a hyperactivity of the skin function, as in perspiration, the toxic products are eliminated in the vapor or moisture of the perspiration, but during a diminution of this function they form the psoriatic patches. When the skin function is increased, as in sweating, a number of products that are otherwise eliminated through the urine pass through the skin, which may eliminate a considerable part of the solid waste products, and particularly a very important chemical product—common salt. When the kidney is diseased the elimination of common salt and other substances may become difficult, and thus still more injure the kidneys; these products, and especially the common salt, will be retained. Then comes the skin to the assistance of the kidneys. Not an inconsiderable part of these substances may then pass through the skin when it is in a condition of increased activity, in the form of sweat. Thus the kidneys and skin work in harmony; they are companions, and may be graphically called “Kidney and Co.,” the skin being the second partner. The skin is thus one of our most important organs, and in the following chapter we will deal with its hygiene. ------------------------------------------------------------------------ CHAPTER XXIV. THE HYGIENE OF THE SKIN—AIR BATHS. IN another part of this work we have attributed to the kidneys a very important part in the causes of premature old age, as their degeneration is one of the most striking causes of auto-intoxication, the immediate cause of old age. The more injurious the products passing through the kidneys, the quicker will these noble organs be degenerated and the sooner will they decay.